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Tuesday, June 5, 2018

All About Soya Bean : To eat or not to eat?

Don't throw the baby out with the bathwater. Don't throw the baby out with the bathwater is an idiomatic expression for an avoidable error in which something good is eliminated when trying to get rid of something bad, or in other words, rejecting the favorable along with the unfavorable.

Soy is definitely one of the most controversial foods in the world.

Depending on who you ask, it is either a wonderful superfood or a hormone disrupting poison.

As with most things in nutrition, there are good arguments on both sides.

What is Soy and How is it Used?

Soybeans are legumes that originated in East Asia, but are now being produced on a large scale in the United States.

Soy is used to make many different foods. Soybeans can be eaten whole, with the immature types being called edamame. Soybeans must be cooked, as they are poisonous when raw.

Soy is used in tofu, soy milk and various dairy and meat substitutes. It is also used in fermented foods like miso, natto and tempeh, which are commonly consumed in some Asian countries.

Over 90% of soy produced in the U.S. is genetically modified and the crops are sprayed with the herbicide Roundup, which may be associated with adverse effects on health (1).

Interestingly, whole soybeans are rarely consumed in Western countries. The majority of soy in the diet comes from the refined products that are processed from the soybeans.

Most of the soy crop in the U.S. is used to produce soybean oil, which is extracted using the chemical solvent hexane. Soybean oil supplied about 7% of calories in the U.S. diet in the year 1999 (2).

What remains of the soybean after the fat has been extracted is called soybean meal, which is about 50% protein. The majority of soybean meal is used to feed livestock, but it can also go through further processing to produce isolated soy protein.

Because it’s cheap and has certain functional properties, soybean oil and soy protein have found their way into all sorts of processed foods, so most people in the U.S. are consuming significant amounts of soy without even knowing about it.

Soy protein is also the major ingredient in soy-based infant formula.

Bottom Line: Most soy in the U.S. is used to make soybean oil. The waste product is then used to feed livestock or processed to produce soy protein. Whole soybeans are rarely consumed.

This portion of soybeans also contains 173 calories, with 9 grams of fat, 10 grams of carbs (6 of which are fiber) and 17 grams of protein (4).

The respectable amount of nutrients needs to be taken with a grain of salt, because soybeans are also very high in phytates, substances that bind minerals and reduce their absorption.

Soybeans are a pretty good source of protein. They’re not as good as meat or eggs, but better than most other plant proteins. However, processing soy at a high temperature can denature some of the proteins and reduce their quality.

The fatty acids in soybeans are mostly Omega-6 polyunsaturated fats. This can be problematic because too many Omega-6s in the diet can lead to inflammation and all sorts of health issues (5, 6).

For this reason, it is very important to avoid soybean oil (and other vegetable oils high in Omega-6) and processed foods that contain it.

Be aware that the nutrient composition of soy depends dramatically on the type of soy food. Whole soybeans can be nutritious, while refined soy-derived products like soy protein and soybean oil aren’t nutritious at all.

Bottom Line: Whole soybeans are rich in micronutrients, but they also contain phytates which block absorption of minerals. Soybeans are very rich in Omega-6 polyunsaturated fatty acids, which can cause problems.

Soy May Have Some Health Benefits

It wouldn’t be right to talk about all the bad stuff without mentioning the good. The truth is that there is some evidence of health benefits in certain people.

Soy has been well researched for its cholesterol lowering effects and several studies show that soy protein can reduce Total and LDL cholesterol, although others find no effect (7, 8, 9, 10).

It’s important to keep in mind that even IF soy reduces cholesterol (which studies don’t agree on), there is no guarantee that this will lead to a decrease in heart disease.

Observational studies show a mixed bag of results. Some studies show a reduced risk of heart disease, others do not (11, 12).

There are also some observational studies showing that soy can reduce the risk of prostate cancer in old age, which is the most common cancer in men (13, 14).

Bottom Line: There is some evidence that soy can lower cholesterol levels, although studies show conflicting results. Men who consume soy are at a lower risk of developing prostate cancer in old age.

Soy Contains Isoflavones That Function as Endocrine Disruptors

Estrogens are steroid hormones mostly found in females, where they play a major role in regulating sexual development and reproductive cycles.

The way estrogens (and other steroid hormones) work, is that they travel into the nuclei of cells and activate the estrogen receptor.

When that happens, there are changes in gene expression, leading to some kind of physiologic effect.

The problem with the estrogen receptor is that it isn’t very selective in the substances that can activate it. Some substances in the environment that look like estrogen can activate it too.

This is where the whole soy thing gets interesting…

Soy contains large amounts of biologically active compounds called isoflavones, which function as phytoestrogens… that is, plant-based compounds that can activate estrogen receptors in the human body (15).

These isoflavones are classified as endocrine disruptors, chemicals that interfere with the normal function of hormones in the body.

The key isoflavones in soy are genistein, daidzein and glycitein.

This can cause reduced estrogen activity due to the isoflavones blocking the actual, more potent estrogen from binding, or it can lead to an increased estrogen activity due to the isoflavones activating the receptors (16).

Bottom Line: The isoflavones found in soy can activate and/or inhibit estrogen receptors in the body, which can disrupt the body’s normal function.

Soy Isoflavones May Affect The Risk of Breast Cancer

Due to the estrogenic activity, these isoflavones are often used as a natural alternative to estrogenic drugs to relieve symptoms of menopause.

In fact, isoflavones can reduce symptoms when women are going through menopause, as well as reduce the risk of bone loss in elderly women, just like estrogen replacement therapy (17, 18).

However, this use is controversial and many believe that the risks outweigh any potential benefit.

Animal studies show that soy isoflavones can cause breast cancer (19, 20, 21). There are also human studies showing that soy isoflavones can stimulate the proliferation and activity of cells in the breasts.

In one study, 48 women were split into two groups. One group ate their normal diet, the other supplemented with 60 grams of soy protein.

After only 14 days, the soy protein group had significant increases in proliferation (increase in number) of the epithelial cells in the breasts, which are the cells that are most likely to turn cancerous (22).

In another study, 7 of 24 women (29.2%) had an increased number of breast epithelial cells when they supplemented with soy protein (23).

These changes may indicate an increased risk of breast cancer, which is the most common cancer in women. However, many observational studies show that women who consume soy actually have a reduced risk of breast cancer (24, 25).

It is a good idea not to make decisions based on observational studies… which tend to be unreliable. The biological changes in the breasts and the studies where soy causes breast cancer in rodents are a major cause for concern.

There are also some small human studies where soy caused mild disruptions of the menstrual cycle, leading to delayed menses and prolonged menstruation (26, 27).

Bottom Line: Soy isoflavones can increase the multiplication of cells in the breasts. However, observational studies show a reduced risk of breast cancer. Soy may lead to mild disruptions of the normal menstrual cycle.

Soy, Testosterone and Male Reproductive Health

Even though men have some amount of estrogen, having significantly elevated levels is not normal.

Therefore, it seems logical that increased estrogen activity from soy isoflavones could have some effects on men.

In rats, exposure to soy isoflavones in the womb can lead to adverse effects on sexual development in males (28, 29).

In one human study, 99 men attending an infertility clinic were studied. The men that had eaten the most soy for the past 3 months had the lowest sperm count (30).

Of course, this study is just a statistical correlation and does not prove that it was the soy that lead to decreases in sperm count.

Another study found that 40 milligrams per day of soy isoflavones for 4 months had no effect on hormones or semen quality (31).

Many believe that soy can reduce testosterone levels, but the effect appears to be weak and inconsistent. Some studies show a small reduction, while others find no effect (32, 33).

Bottom Line: Exposure to estrogen-like compounds in the womb can lead to adverse effects on males. Studies on the effects of soy on testosterone and sperm quality are inconclusive.

Soy May Interfere With The Function of The Thyroid

The isoflavones in soy also function as goitrogens, which are substances that interfere with thyroid function.

They can inhibit function of the enzyme thyroid peroxidase, which is essential for production of thyroid hormones (34, 35).

Many subjects experienced symptoms of hypothyroidism, including malaise, constipation, sleepiness and thyroid enlargement. These symptoms went away after they stopped consuming the soybeans (36).

However, there are other studies showing that soy has either no effect or only a very mild effect on thyroid function in humans (37, 38, 39).

Bottom Line: Even though soy isoflavones have been shown to inhibit the function of a key enzyme in the thyroid, there is not enough evidence to conclude that they contribute to hypothyroidism in adults.

Soy-Based Baby Formula is a Bad Idea

Exposing infants to isoflavones by feeding them soy-based infant formula can have harmful effects.

In one study, infant girls fed soy formula had significantly more breast tissue at 2 years of age than those who were fed breast milk or dairy-based formula (40).

Another study showed that girls fed soy formula were much more likely to go through puberty at a younger age (41).

There is also evidence that soy formula during infancy can lead to a lengthening of the menstrual cycle and increased pain during menses in adulthood (42).

Soy is also very high in manganese, MUCH higher than breast milk, which may lead to neurological problems and ADHD (43, 44). Soy infant formula is also high in aluminum, which can cause all sorts of problems (45, 46).

There is no question about it… breast milk is by far the best nourishment for babies. For women who can not breastfeed, milk-based formula is a much better option than soy-based formula, which should only be used as a last resort.

Bottom Line: There is significant evidence that soy-based infant formula can cause harm, both via its isoflavone content and its unnaturally high content of manganese and aluminum.

Fermented Soy May be Safe in Small Amounts

It is true that many Asian populations have consumed soy without apparent problems.

In fact, these populations tend to be much healthier than Westerners, although they’ve started to suffer many of the same diseases now that the Western diet has invaded those countries.

The thing is… these populations usually consume fermented soy products like natto, miso and tempeh.

Fermenting soy degrades some of the phytic acid, although it doesn’t get rid of the isoflavones (47).

Natto may be especially healthy, as it also contains a significant amount of Vitamin K2, which is important for cardiovascular and bone health and many people aren’t getting enough of (48, 49).

The dose makes the poison… and phytoestrogens are probably fine if you don’t eat that much. If you’re going to consume soy, choose fermented soy products and use small amounts.

Abstract

BACKGROUND AND AIM:

Vitamin K dependent proteins have been demonstrated to inhibit vascular calcification. Data on the effect of vitamin K intake on coronary heart disease (CHD) risk, however, are scarce. To examine the relationship between dietary vitamins K(1) and K(2) intake, and its subtypes, and the incidence of CHD.

METHODS AND RESULTS:

We used data from the Prospect-EPIC cohort consisting of 16,057 women, enrolled between 1993 and 1997 and aged 49-70 years, who were free of cardiovascular diseases at baseline. Intake of vitamin K and other nutrients was estimated with a food frequency questionnaire. Multivariate Cox proportional hazards models were used to analyse the data. After a mean+/-SD follow-up of 8.1+/-1.6 years, we identified 480 incident cases of CHD. Mean vitamin K(1) intake was 211.7+/-100.3 microg/d and vitamin K(2) intake was 29.1+/-12.8 microg/d. After adjustment for traditional risk factors and dietary factors, we observed an inverse association between vitamin K(2) and risk of CHD with a Hazard Ratio (HR) of 0.91 [95% CI 0.85-1.00] per 10 microg/d vitamin K(2) intake. This association was mainly due to vitamin K(2) subtypes MK-7, MK-8 and MK-9. Vitamin K(1) intake was not significantly related to CHD.

CONCLUSIONS:

A high intake of menoquinones, especially MK-7, MK-8 and MK-9, could protect against CHD ( coronary heart disease ). However, more research is necessary to define optimal intake levels of vitamin K intake for the prevention of CHD.

Take Home Message

Reviewing the evidence on soy is incredibly confusing. For every study showing harm, there is another one showing beneficial effects.

However, I’d like to point out that in every study I looked at that showed beneficial effect, the study was either sponsored by the soy industry, or the authors had some kind of financial ties to the soy industry.

This doesn’t necessarily mean that their studies are invalid, but it’s something to keep in mind.

At the end of the day, it is important for women who are pregnant, plan on becoming pregnant, or are breastfeeding, to avoid soy and other sources of endocrine disrupting compounds.

Avoiding soy infant formula is very important as well. It should only be used as a last resort.

However, the evidence is too weak and inconsistent to conclude that moderate amounts of soy cause harm in adults.

I personally choose to avoid soy… even though the evidence is inconclusive, the fact that it is a relatively new food in the diet that contains endocrine disrupting compounds is reason enough for me.

Baffled by the contradictory reports on soy's health benefits? If you are, it's not surprising, as this is one area of nutrition research that's really led to a boatload of confusion. We know that __soybeans are an excellent source of digestible protein, and are rich in fiber, B vitamins, and alpha-linolenic acid, a precursor to omega-3 fatty acids. But__what are the impacts of eating soy when it comes to heart health, cancer, bone density and more? We're here to separate fact from fiction.

Soy and cancer: When it comes to breast cancer, studies show that consuming as little as one serving of whole soy foods daily throughout childhood and adolescence may reduce breast cancer risk in later life by as much as 50 percent. But that protection hasn't been seen in adults; in fact, some studies suggest that high doses of soy for mature women might actually be harmful, since soy estrogens cause breast cell proliferation, a known risk factor for breast cancer. As for the guys? Studies in Asia show that men who consume two servings of soy daily are 30 percent less likely to have prostate cancer than men who have lower intakes or don't eat soy at all; in addition, preliminary research suggests that soy inhibits the progression of the disease for those who have it. And although the exact role soy plays isn't certain, people living in Asia who eat a diet high in whole soy foods have the lowest rates of breast and prostate cancer in the world, according to Daphne Miller, M.D., author of The Jungle Effect: A Doctor Discovers the Healthiest Diets from Around the World -- Why They Work and How to Bring Them Home.

Soy and your bones: Most studies show that eating soy has zero effect on protecting bones. In fact, all beans -- including soybeans -- contain phytic acid, which is a natural plant substance that blocks calcium (and other minerals) from being absorbed. So excess soy consumption may actually be detrimental in this regard.

Between tofu and tempeh, miso and soy milk, and the ever-popular edamame, there's certainly no shortage of soy on the shelves of your local food store. Long touted by health-minded folks as a better-for-you, eco-friendly alternative to meat, soy is a favorite among followers of increasingly mainstream plant-based diets. Yet, do a quick Google search for "soy" and some of the first results include headlines like, "The Dangers of Soy" and "Is Soy Bad for You?"

So what's the deal? Here's what you should know about the pros and cons of eating soy.

The Benefits of Swapping Hot Dogs for Soy

One of the biggest benefits of eating soy is that it can replace foods that may compromise your health, says Academy of Nutrition and Dietetics Spokesperson Vandana Sheth, RDN, CDE. "If we are talking about soy in its whole form such as edamame, tofu and whole soy milk, then it is healthier than meat in the sense that soy provides an excellent source of protein, fiber, vitamins and minerals — without the cholesterol and saturated fat found in meat," she says.

It's the same rationale the Meatless Monday campaign uses to validate the claim that forgoing meat one day a week can lower your risk for cancer, cardiovascular disease, diabetes and obesity. You're probably (or, hopefully!) swapping out less healthful foods, such as red meat, in favor of plant-based foods. And while there's some evidence that soy might slightly lower your risk of heart disease, the effects are minor — but more on that below.

But Is Soy Really a Superfood?

Aside from the idea that eating more soy might lead you to eat less meat, there's not much evidence that soy itself produces health benefits. Claims that it lowers cholesterol, calms hot flashes, prevents breast and prostate cancer, aids weight loss and wards off osteoporosis are all based on preliminary research, inconclusive evidence or overstated claims according to a 2014 Harvard T.H. Chan School of Public Health report.

For example, while the American Heart Association used to advocate eating soy as part of a "heart healthy diet," they have since backed off that recommendation because the data did not support such a claim, says Heather Patisaul, a developmental biologist at North Carolina State University who has studied the effects of eating soy. "For most people the benefits of soy on heart health are very small: a few cholesterol points but not much else," she notes.

In fact, an American Heart Association review of 22 randomized trials found that eating 50 grams of soy a day only lowers LDL (aka: bad) cholesterol by three percent. To put that in perspective, you'd have to eat one-and-a-half pounds of tofu or drink eight, eight-ounce glasses of soy milk a day in order to consume 50 grams of soy. And that's a lot of tofu, even for the most dedicated of soy fanatics.

The Darker Side of Soy

Soy has a shadier side, too — most notably regarding the effect it may have on your hormones. That's because soy contains isoflavones — a type of phytoestrogren that mimics the effect of estrogen on the body. When you eat lots of soy, it has the potential to disrupt estrogen-sensitive systems in your body, including the reproductive system (which includes the brain, the pituitary gland and the reproductive organs), says Patisaul. There have even been cases where women have eaten so much soy (think: 60 grams a day for a month) that they've temporarily shut down their menstrual cycle, Patisaul says. "The developing brain is also very sensitive to estrogen, as is the mammary gland and the heart," she notes.

It's the same argument you've likely heard against using plastic water bottles containing bisphenol A (BPA), except that soy is even more estrogenic than BPA, according to a review of research on the pros and cons of phytoestrogens by Patisaul and her team. Beyond that, the NIH states that soy's possible role in breast cancer is "uncertain" and advises that, "women who have or who are at increased risk of developing breast cancer or other hormone-sensitive conditions (such as ovarian or uterine cancer) should be particularly careful about using soy and should discuss it with their health care providers."

"Because everybody is different, it is impossible to know what the 'right' amount of soy is, but people can certainly go overboard," says Patisaul. "For people wanting to achieve a reasonably healthy protein intake without experiencing possibly negative effects of soy, there is no need to have soy at every meal or to replace all foods [like milk and cheese] with soy-based ones."

The Takeaway

So should you give up soy for good? Not necessarily. Eating some soy can be a healthy way to cut back on meat while still making sure you're eating enough protein. But too much of a good thing has the potential to take its toll on your hormones and your health. "For healthy adults, I think about soy the way I think about things like sugar, alcohol and caffeine," says Patisaul. "Moderation is key."

How Healthy Is Soy Really?

Soy Healthy Food Guide

Healthy reasons to eat soy.

Soy foods aren’t just for vegetarians anymore. With so many options, from edamame to tempeh, and plenty of health benefits to including soy in your diet, there’s every reason to enjoy them.
According to a 2005 study by the U.S. Soybean Board, 30 percent of Americans consume soyfoods or beverages at least once a month. Tofu is an economical, low-fat and cholesterol-free protein source. And consuming 25 grams of soy protein a day (about 1 1/4 cups of tofu or edamame or 3 1/2 cups soymilk) may help reduce risk of heart disease by lowering cholesterol levels.
There are several soy-based options beyond tofu. Try tempeh—a soybean loaf with a heartier texture than tofu. Soymilk works deliciously in breakfast smoothies or nondairy “milkshakes.” Add edamame (fresh soybeans) to salads and stir-fries. Roasted soy nuts can be used in trail mix or eaten on their own as a crunchy snack. Or use soy sauce and miso to flavor food with the dark, earthy flavors so familiar in Asian cuisine.

Why soy is good for you

What you get: This versatile bean is best known for delivering a healthy amount of protein, and any form of the bean—be it edamame, tofu, tempeh, soy nuts or ground soy isolates used to make soy burgers—is an excellent plant source of high-quality protein. In addition, soy delivers fiber, some iron and the phytoestrogens daidizein and genistein, which are thought to have a wide range of health benefits for heart health and menopausal symptoms.

How to Shop for Soy

Shopping Tips:
•Edamame are fresh soybeans that look like bright green lima beans. Their flavor is sweet and mild, with a touch of “beaniness.” Edamame are found in the natural-foods freezer section of large supermarkets and natural-foods stores, sold both in and out of the “pods.” One 10-ounce bag contains about 2 cups of shelled beans. Look for fresh ones at farmers’ markets or natural-foods stores.
• Miso is fermented soybean paste made by inoculating a mixture of soybeans, salt and grains (usually barley or rice) with koji, a beneficial mold. Akamiso (red miso), made from barley or rice and soybeans, is salty and tangy, and the most commonly used miso in Japan. Use in marinades for meat and oily fish, and in long-simmered dishes. Shiromiso (sweet or white miso), made with soy and rice, is yellow and milder in flavor; use for soup, salad dressings and sauces for fish or chicken. Look for it in the natural-foods section of most supermarkets and in Asian markets.
• Soy flour is made from mature soybeans that have been dried, hulled, split and ground into flour. The texture is denser than wheat flour and it has a pronounced flavor some describe as “beany.” It is available in both full-fat and defatted varieties. Look for soy flour in natural-foods stores.
• Soy nuts are mature soybeans that have been soaked then roasted, either in oil or using a dry-roasting process. Crunchy, with a texture like crumbly peanuts, they’re often creatively flavored.

More Tips for Shopping for Soy

• Soy sauce is a dark fermented liquid made from soybeans. It can be found in the Asian section of most supermarkets, in natural-foods stores or Asian grocery stores.
• Soymilk is a dairy-free milk made from pressed, cooked and ground soybeans. It can be found in natural-foods stores and in most supermarkets in the dairy case or on shelves in aseptic packaging.
• Tempeh is a chewy, nutty, fermented soybean loaf. Find it (plain or with added grains) near refrigerated tofu in natural-foods stores and many large supermarkets.
• Tofu is “soybean curd” made by heating soymilk and a curdling agent in a process similar to dairy cheesemaking. The longer the pressing, the firmer and denser the tofu. Silken tofu is delicate and custardlike, perfect for pureeing and using in dressings, smoothies, sauces or floating in delicate soups. Extra-firm tofu is ideal for stir-fries, sautés and grilling, while the soft variety makes a good substitute for ricotta in Italian dishes or for eggs in quiches. Firm tofu is a good all-purpose choice. Tofu is available at natural-foods stores and most large supermarkets. Look for water-packed tofu in the produce section and aseptic-packaged tofu with other Asian ingredients.

Storage Tips for Soy

• Fresh and cooked edamame should be stored in the refrigerator or freezer.
• Miso keeps for months in the refrigerator.
• Full-fat soy flour can go rancid quickly; keep it in the refrigerator for up to 6 months or in the freezer for up to 1 year. Defatted soy flour can be kept unrefrigerated.
• Store soy nuts in the refrigerator for up to 3 months after opening.
• Soy sauce should be refrigerated after opening.
• Unopened aseptically-packaged soymilk can be stored at room temperature for several months. Refrigerated soymilk should be stored in the refrigerator. Opened soymilk should be stored in the refrigerator and should stay fresh for 5 days.
• Store tempeh wrapped in plastic in the refrigerator for up to 5 days after opening.
• Tofu will last 5 to 7 days after opening. Store in a loosely sealed container of water in the refrigerator, changing the water daily. You can also freeze tofu for up to 5 months. (Don’t be surprised if the frozen tofu turns a light shade of caramel and has a slightly chewier texture.)

A Fun Fact About Soy

The United States is the world’s largest producer of soybeans.

Banana-Cocoa Soy Smoothie

With plenty of protein from both tofu and soymilk, this banana-split-inspired breakfast smoothie will keep you satisfied until lunchtime. Banana-Cocoa Soy Smoothie

Edamame Succotash with Shrimp

We give succotash—traditionally a Southern dish made with corn, lima beans and peppers—an update using edamame instead of limas and turn it into a main dish by adding shrimp. To get it on the table even faster, purchase peeled, deveined shrimp from the fish counter instead of doing it yourself. Make it a meal: All you need is a warm piece of cornbread to go with this complete meal. Edamame Succotash with Shrimp

Egyptian Edamame Stew

A riff on the Egyptian classic ful medames, a highly seasoned fava bean mash, this version is made with easier-to-find edamame. Edamame (fresh green soybeans) have been shown to lower LDL cholesterol. They can be found shelled in the freezer section of well-stocked supermarkets. This stew is great served with couscous, bulgur or warm whole-wheat pita bread to soak up the sauce. Egyptian Edamame Stew

Tofu Parmigiana

Instead of having a greasy, battered coating, the tofu “steaks” in our revamped Parmigiana are breaded and lightly pan-fried in just a small amount of oil then topped with part-skim mozzarella, fresh basil and your favorite marinara sauce. This Italian classic will please even those who are tofu-phobic. Tofu Parmigiana

Broiled Salmon with Miso Glaze

Versatile miso (fermented soybean paste) keeps for months in the refrigerator and adds instant flavor to soups, sauces, dips, marinades and salad dressings. In general, the lighter the miso, the milder and sweeter its flavor. Light miso is the key to the wonderful flavor of this salmon. Broiled Salmon with Miso Glaze

Miso-Glazed Peas & Carrots

This sweet, salty and tangy twist on the old standby vegetable combo is sure to please the whole family. Miso-Glazed Peas & Carrots

Savory Orange-Roasted Tofu & Asparagus

If you've never had roasted tofu before, here's a great way to start. Toss tofu and asparagus in a tangy orange- and basil-scented sauce, made rich and savory with miso. Serve with brown rice or couscous and an orange-and-fennel salad. Savory Orange-Roasted Tofu & Asparagus

More Delicious Recipes with Soy

When it comes to breast

cancer: is soy safe?

By: Brierley Wright, M.S., R.D.

Last week I blogged about what to eat right now for better breast health. I received a lot of comments—and concerns—from readers, mostly on the topic of soy. A few months ago, I too started wondering about the connection between soy and breast health. Soy is touted as a food that can prevent breast cancer—and also implicated as one that might promote it. In the last year, I’ve increased how much soy I eat each week because I’ve been eating a more vegetarian-based diet. So, I wanted to know what the science said: is soy safe or not?

Here’s what I found.

• Researchers still don’t know whether isoflavones—the compounds in soy that act as weak estrogens in the body—spur the growth of tumors by acting like estrogen or prevent breast cancer by competing with the breast’s natural estrogen. Scientists who looked at the effect individual isoflavones from soy had on breast-cancer cells in test tubes have found both results.

• Recent studies, however, which looked at dietary habits, are helping scientists to better understand who might reap the greatest protection from soy. One study of nearly 74,000 Chinese women, age 40 to 70, found those who consumed a daily serving or more of soy had a significantly lower risk of developing breast cancer in their premenopausal years than women who ate soy less frequently. Also in this study, the women who started eating soy consistently in adolescence had an even lower risk than those who started later. However, in this study eating soyfoods did not protect women from developing breast cancer after menopause.

• Studies are conflicting about the benefits of soyfood consumption later in life. Researchers hypothesize that in younger women, when the body’s estrogen levels are high, isoflavones in soy may compete with the body’s natural estrogen and reduce risk of breast cancer. After menopause, however, natural estrogen levels are much lower and so it’s thought that the isoflavones act like estrogen. Higher estrogen levels are linked with higher risk for breast cancer. That doesn’t mean that eating soyfoods like tofu and edamame—in moderation—after menopause is unsafe, as there’s no data to show that eating soyfoods increases breast-cancer risk in postmenopausal women.

The Bottom Line: Adding soy to your diet in midlife might not offer much protection against breast cancer. But it probably won’t hurt either: soyfoods are a healthy, protein-rich, low-saturated-fat alternative to foods like red meat. Because theoretically soy isoflavones can act like estrogen, it’s best to eat soyfoods in moderation at any age—up to two servings daily, which is equivalent to 1/2 cup tofu or edamame and 1 cup soymilk.

As the soya debate rages on, Nutrition Editor Eve Kalinik clears up the pros and cons of this surprisingly nutritious and natural food.

There is no doubt that soya is a highly controversial food – but, like many aspects of nutrition, it is rarely that straightforward. When we look at any food, we almost always have to consider the ancestral history to get a true and meaningful understanding of how it has always been consumed, and this is most certainly the case with soya.

Traditionally, a soya-based food, such as tofu, is served in small amounts and combined with other foods to make it more easily digestible. Moreover, in its original East Asian cuisine, the beans are usually fermented to create foods like tempeh, soy sauce, natto and miso, and soya is typically eaten in its fermented form.

Why? Well, these guys understood that soya in its natural state, just like other legumes, contain substances, such as enzyme inhibitors and phytic acid, that can make it difficult to digest and also impair the uptake of certain nutrients. However, when soya is fermented, this largely negates or removes these substances, releasing all of its bountiful nutrition. The problem is that so much of the commercial soya we see in our supermarkets is highly processed without these traditional methods.

Plus, the sheer volume of huge lattes, its liberal addition to cereals and the fact that soya crops up in so many other foods, such as salad dressings and chocolate, often in the form of lecithin, means we are eating way more than we think, and that’s never how it was meant to be consumed.

The other issue with having very large concentrations of soya is that it has natural phyto-estrogenic properties, and can mimic the effects of oestrogen. That’s before we get into the environmental impact and the effect producing all these soya products has on our planet.

However, with that being said, eaten in its traditional and fermented form, soya provides an excellent source of protein, calcium, iron, magnesium and natural probiotics; it’s all about enjoying its distinct umami flavour and nutritional benefits as part of a diverse and varied diet.

My soya top picks

Miso Tasty Miso Paste – Organic, unpasteurised miso paste that has been fermented, and is also brimming with natural probiotics (misotasty.com).

Clean Bean Tofu – Organic, non-GMO tofu that has been produced the traditional way (cleanbean.co.uk).

Impulse Tempeh – Organic, fermented soy beans that are a great way to extend your meat-free repertoire (impulsefoods.co.uk).

While soybean products can be a healthy part of a vegetarian or traditional diet, there are several pitfalls to watch out for. One factor is whether the soybeans are genetically modified. Another is where they were grown (some companies who pose as organic purveyors refuse to disclose their sources). Especially important in considering soybean pros and cons is whether the final product was fermented or not. This article will explain the many details of soybean products.

Soybean – Glycine max (Fabaceae)

An oilseed legume native to East Asia, soybeans have been cultivated for over 3000 years, and are the most widely consumed legume in the world. Soybeans contain large amounts of molybdenum, tryptophan, and manganese along with protein, iron, omega 3 fatty acids, phosphorous, copper, potassium magnesium and vitamins B12 and K. Soybeans also contain isoflavones, antioxidants that help lower cholesterol. Soy helps lower blood pressure, is anti-inflammatory, and has cardio protective effects. Soybeans are considered especially healthy for women because the phytoestrogens in soy help increase bone density. However, phytoestrogens are of questionable benefit to men and may elevate unwanted estrogen. A large percentage of soybeans in the US come from Genetically Modified seeds, so organic soybeans are recommended. Soybeans contain goitrogens which may have negative consequences on the thyroid and may be a cause of thyroid cancer.

The Fermentation Process

Fermentation is the most important factor in whether or not soybean products are healthy. Unfermented soybean products should be avoided as they contain phytate, also known as phytic acid, a compound that robs the body of minerals.

Soybean products are fermented by two types of molds:

* Koji – Aspergillus Oryzae (Trichocomaceae)

Koji is the mold used to ferment many Japanese foods, including tamari, miso and mirin (the rice vinegar used to flavor teriyaki sauce and ponzu sauce). Koji contains amylase, an enzyme that helps in the digestion of carbohydrates. Koji contains the amino acid glutamate, a natural concentrated salty flavor (known as the sixth taste or umami).

The mold used in the production of tempeh, Rhizopus oligosporus is edible and doesn’t produce any known toxins. Producing a white, fluffy mycelia, Rhizopus contains a natural antibiotic that inhibits dangerous bacteria including Staphyloccus aureus. This is one reason tempeh is believed to reduce intestinal infections. There is no record of illness resulting from the consumption of tempeh.

Recommended Soy Products

First the good news: there are three popular fermented products you can enjoy which are outlined in this section.

* Miso

Miso is a fermented soybean paste originating in Japan that is becoming popular in the West. Miso has a salty, buttery taste and can be used as a versatile condiment for a variety of recipes or as a soup base. Miso by itself is an antioxidant and is made by fermenting soybeans with the Koji mold. Miso contains vitamin K, B6, B12, calcium, iron, zinc, phosphorous, copper and is loaded with protein and amino acids. It does contain a good amount of sodium. Those looking to stock up on quality food should store some miso paste. Twelve ounces of miso paste is enough to make several gallons of delicious soup and it is live food, not sterile the way canned soups are.

* Tempeh

Tempeh is made by fermenting soybeans with the Rhizopus mold. Tempeh contains antioxidants, isoflavones and soy saponins along with fiber, complete protein and every essential amino acid. Tempeh aids digestion and boosts the immune system while providing an easily assimilated protein in vegetarian form.

* Tamari ( Real Soy Sauce)

Tamari is a concentrated, fermented soy product that has been used in China for nearly 3000 years. Tamari is rich in antioxidants and is a good source of the amino acid tryptophan. Tamari also contains vitamin B6, iron, phosphorous, and protein. Contrary to popular belief, soy sauce should be refrigerated after opening.

Soy Products to Avoid

Now the bad news: While risking offending proud members of the Soybean Association, this author feels the following two products should be avoided.

* Tofu

Tofu is unfermented soybean curd. Though it contains protein it is difficult for some to digest and may disrupt or interfere with normal hormones due to estrogen mimicking compounds, and compromise body mineralization. Thus tofu has questionable health benefits.

* Soy Milk

There are numerous reasons to avoid soy milk besides the taste. Since it is unfermented it also contains mineral robbing phytate and a high level of phytoestrogens. Only two glasses of soy milk per day for one month contains enough of these hormone-like substances to change the timing of woman’s menstrual cycle. 100 gm of any soy product contains as much estrogenic content as a contraceptive pill.

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What exactly is soy?

Soy – or soya – is a bean with many guises. It can be eaten fresh from the pod (known as an edamame bean); unfermented as soya milk and other dairy alternatives, tofu (bean curd) and meat replacements, such as mince and textured vegetable protein (TVP); and fermented as tempeh (bean cake) and miso (bean paste).

What are soy's main health benefits?

'It's an excellent source of protein, so can be especially beneficial for vegetarians and vegans, who don't eat any animal protein,' says Rob Hobson, registered nutritionist at Healthspan and co-author of The Detox Kitchen Bible. 'It also contains calcium, which is needed for good bone health, so may be of particular benefit for post-menopausal women, who can lose up to 10 per cent of their bone density.'

The best foods to eat for bone health
But calcium isn't the only bone-building hero found in soy: it's also the main dietary source of plant chemicals called isoflavones, which are similar in structure to the human hormone oestrogen. A diet rich in soy proteins and isoflavones can significantly improve bone health and reduce risk of osteoporosis after the menopause, according to a recent study at the University of Hull.

Best and worst foods for hot flushes
Soy is also a good source of essential minerals including iron, magnesium and potassium, as well as vitamins B6, E, K and folate. It's naturally low in saturated fats and sodium, and has a low glycaemic index, which means soy carbohydrates are released slowly and steadily to help keep blood sugar levels steady.

Great! Anything else in soy’s favour?

Some researchers have suggested that soy isoflavones can help reduce menopausal hot flushes. However, a recent British Pharmacological Society study review concluded that these positive effects were generally 'slight and slow' – so nothing to get too excited about.
There's also good evidence that soy may slightly reduce levels of heart-harming LDL cholesterol.More cholesterol-lowering foods

OK, so what about all these soy scare stories?

'Much of the controversy surrounding soy is related to breast cancer risk and treatment,' Hobson explains. 'But the consensus from the available research is that consuming moderate amounts of soy – one to three servings daily – as part of a balanced diet is fine.'
Admittedly, though, the available evidence can be confusing.

Recent research at Georgetown University Medical Center in the US suggests that long-term soy consumption may improve the effectiveness of a common breast cancer treatment, tamoxifen, and reduce recurrence. But eating soy for the first time while being treated with tamoxifen can lower its effectiveness and increase chances of the disease recurring. So do ask your doctor's advice before consuming soy if you're receiving breast cancer treatment.
'Soy isoflavones have also been linked to hypothyroidism as they may inhibit the function of a key enzyme in the thyroid,' says Hobson. 'But much more research is needed on this.'

Anything else I should be worried about with soy?

Some of the other plant chemicals found in soy, such as phytates and oxalate, can sometimes inhibit the absorption of minerals, including calcium, iron and zinc. However, recent studies show these minerals are usually well absorbed from soya when eaten as part of a healthy, balanced diet. What's more, the phytate content can be significantly reduced during the fermentation process – so it's not always a concern.

How does soya milk compare to cow's milk?

'Always choose a soya milk that's been fortified with vitamins and minerals, such as bone-building vitamin D,' Hobson advises.'Other than that, soya milk contains around the same amount of calories, but less fat and protein than semi-skimmed milk. Cow's milk contains more vitamin B12, which is essential for brain health, than soya milk and around the same amount of calcium.'

So it's OK to keep soy on my shopping list then?

'Yes,' says Hobson. 'But do opt for soy foods that aren't genetically modified or overly processed. Fermented varieties, such as miso and tempeh, appear to be the most beneficial, but all can still offer a healthy contribution to your diet.'

Soy has gone mainstream in the U.S. Toddlers snack on edamame, Chipotle sells spicy marinated tofu burritos, and plenty of people can’t start their day without a large soy-milk latte. But is soy all it’s cracked up to be—and is there any basis to concerns that the isoflavones in soy may contribute to cancer? We looked at the complicated, controversial, and ever-evolving research on soy and our health.

The good news about soy

It’s heart-healthy. Soy protein has been shown to slightly reduce levels of LDL cholesterol, the “bad” kind. A landmark 1995 study that looked at nearly 40 controlled clinical trials found that replacing 50 grams of animal protein a day with 50 grams of soy protein lowered LDL cholesterol by nearly 13 percent. But a subsequent American Heart Association update found that the reduction is actually closer to 3 percent—not to mention the fact that to get 50 grams of soy protein you’d need to eat about a pound of tofu or drink a half gallon of soy milk. That said, replacing even a small amount of your daily animal protein with soy protein is smart for your heart and blood vessels, as it’s leaner than many animal protein sources—plus the fat it does contain is the heart-healthy type. Soy also supplies fiber, vitamins, and minerals. If a food contains at least 6.25 grams of soy protein per serving and is low in saturated fat and cholesterol, the FDA permits it to carry the claim that consuming “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.” It’s a stellar protein source. One cup of unshelled edamame, for example, packs 17 grams of protein, almost as much as three ounces of 70 percent lean ground beef and about the same as a hard-boiled egg. Soy is also unusual in that it’s a complete protein source, meaning it contains all of the essential amino acids rather than just some of them, as most plant sources do. It’s high in fiber. One cup of cooked edamame contains 8 grams of fiber, as much as a dozen prunes. It’s an alternative to cow’s milk. One cup of soy milk offers nearly as much protein as the same amount of dairy milk and, if fortified with calcium, supplies up to 30 percent of your daily calcium requirement (the exact amount varies by brand). Note that not all soy milk is fortified; check the label if you want to ensure that calcium and vitamins A and D have been added. Also check the label for sugar content, since some soy milk has a lot of added sugar. Or opt for unsweetened varieties.

The maybe good news about soy

The isoflavones in soy may strengthen your bones... Isoflavones are a type of phytoestrogen, meaning they are plant-derived compounds that weakly mimic the effect of estrogen. Because estrogen plays a role in bone health, it’s been suggested that soy isoflavones may reduce osteoporosis risk. But the evidence for this is mixed; some studies have found that women nearing menopause who consume soy protein are more likely to increase their bone density than women whose diets lack soy isoflavones, but other studies have found no impact. …or help with hot flashes. Research on soy’s effect on hot flashes has been similarly mixed. The North American Menopause Society’s 2015 position statement on nonhormonal treatment of hot flashes says that supplements containing soy isoflavones may help, but more research is needed. And some evidence suggests that the supplements may increase breast cancer risk, as discussed below, so for now we think it's prudent to avoid them.

Safety concerns about soy

Because soy can mimic the activity of estrogen in the body, there has been some concern that it might increase breast cancer risk. The type of soy that’s potentially worrisome is supplemental soy and soy protein isolates, the kind used in nutritional bars and supplements. In fact, the phytoestrogens (estrogen-like compounds) in whole soy foods mayactually help protect against breast cancer.The American Cancer Society says that more research is needed to understand the relationship between specific forms of soy and cancer risk. According to a statement on the organization’s website, “moderate consumption of soyfoodsappears safe for both breast cancer survivors and the general population, and may even lower breast cancer risk.” It advises avoiding soysupplements, however,until more research is done. That view is echoed by Patty Siri-Tarino, PhD, a nutrition researcher at the Children’s Hospital of Oakland Research Institute and member of our editorial board. She points out that studies of soy isoflavone supplementation have not supported health benefits, and some studies (mostly in animals) even suggest potential harm. “Everyone should aim to get their isoflavones from real food,” she says. The epidemiological studies that suggest health benefits of soy, particularly in Asian populations, pertain to soy consumed in foods, not supplements. Plus, foods like edamame offer more than just isoflavones, including fiber, vitamins, and minerals. For other top food sources of soy, see the list below. Hexane in processed soy foods is another concern. Hexane is a solvent used to extract oil from soybeans. If your bar or meat substitute has soy protein isolate, soy protein concentrate, or textured vegetable protein listed on its label, it likely has undergone hexane processing. Hexane is classified as a neurotoxin by the CDC, and chronic exposure in factory workers has been linked to neurological conditions. But it’s unclear whether consuming trace residues is hazardous. If you’d like to avoid hexane-treated soy foods, look for products with the USDA organic seal, as hexane is banned in organic food production. Better yet, buy soy foods made from whole soybeans—such as tofu, tempeh, soy milk, and soy yogurt—since they don’t typically undergo hexane processing and are generally healthier for you, too. Whole soybeans (edamame) are always a hexane-free and healthy option.